The present invention generally relates to spool structures such as are used to wind and transport great lengths of communication and power transmission cable.
Cable is a term used in many industries to describe a rope-like structure that is relatively flexible, has a substantially constant cross sectional shape and an indefinite length. Communications cable may be a fiber optic wave guide within a protective sheath or one or more insulated electrical conductors. Such communication cable is generally produced as a continuous process having a substantially uniform surface texture and circular cross-sectional shape. Since the production is continuous, the length of such cable is determined most often by the length of a manageable quantity, whether in terms of weight or volumetric bulk. Commercial power transmission cable and bundled trunk lines of communication cable are generally wound on large spools of several thousand pounds or more and suitable for handling only by heavy duty power equipment.
The basic construction of an electric conductor or optical wave guide cable spool comprises a substantially cylindrical hub having a surface perimeter that is generally equidistant radially from an elongated hub axis. A convenient axial length of the hub is terminated at opposite axial ends by respective radial flanges. These flanges are generally circular about a center at the hub cylinder axis. The inside or oppositely facing surfaces of these spool flanges generally lie in a plane that is normal to the hub cylinder axis.
One of the characteristics distinctive to the power and communications industries is the need to verify, often frequently, the continuity of cable wrapped upon a transport spool. Hence, physical access to that end of the cable starting the spool wrap is essential. Traditionally, access to the starting end of the cable is assured by securing the starting end to the outer perimeter of one spool flange. From the flange outer edge, the cable lies contiguously with the inner face of the flange along a tangent course with the reel hub perimeter. From tangency with the reel hub, rotational wrapping about the hub begins and progresses along the axial length of the hub to the opposite end flange. Here, the winding cable length begins to overlie those wraps below and proceeds with a second layer of side-by-side wraps progressing along the axial length of the hub back toward the first flange.
This progression continues, layer upon layer, until the desired cable length is wound upon the spool frame. Due to the presence of the cable starting end lying against the inside face of the first flange, a discontinuity is presented along the axial space between the opposite flange faces. This discontinuity allows for one less wrap about the spool hub perimeter along a line between the starting end of the cable and the opposite flange face as compared to the remainder of the hub length between opposite flanges.
One consequence of this hub length discontinuity presented by physical access to the cable starting end is a sliding and often abrasive contact between cable surfaces during the unreeling process as an unwinding wrap slides against the starting end of the cable. Additionally, this discontinuity in the distance between opposing flange faces disrupts the uniform tension and order in the lay of the wrap about the spool hub.
One prior art approach to this wrap discontinuity issue has been to provide a channel in the inside face of one flange to receive the starting cable end. This solution, however, significantly increases the spool construction cost. Another prior art solution has been to secure a layer of inexpensive material against the inside face of the first flange to provide a false inside face for the first flange that includes a protective channel for receipt of the cable starting end. The material substance of such a false face may be soft and inexpensive such as foamed plastic sheet.
A major difficulty with plastic foam sheet for this purpose has been the inability to store the article prior to use in a nested condition. Additionally, such materials generally are somewhat fragile and easily broken.
It is, therefore, an object of the present invention to provide a spiral course reel guide that may be transported and stored in a densely packed, nested condition.
Another object of the invention is provision of a spiral reel guide that is vacuum formed from a single sheet of tough and resilient thermoformed plastic.